Plastic molding apparatus



'vl-May-IS, 1943` A. A." BURRY v$519,439

PLASTIC MOLDING A APPARATUS Filed Deo. 11,f 19s9` s sheets-sheet 2 'moredependable and l achieved. l l t i The principal feature of the presentinvention`` residesbroadly in the' novel combination fwith eirthe une ore i Lllgure 6 'is' 'a longitudinal midg-sectio'nal elevay e tionillustrating a modiilc'ation of thefpresent r tio'hfoi aj of Figure "7.

`l VApplication`l`)eeein"ber 11. Masern: Nestasie u f chiesto iinvention relates "to injection molding in which al plastic in Vheatedformisfforced throzhw e an injection V,or extruding` orifice anddtisanimportant fobject of the present inyentionfto; 1 ensure'a more uniformdistribution and accurate" t outer control of,` the plasticizingVtemperaturen whereby uniformes-ebs 'Win11 be the "injection cylinder ofa heating"jaclretsurfiV n {In the drawings Finire 1 is e mid-sectional'-eievetiohei `view e illustrating the present invention'in combination-with anl injectic'in cylinder.

"Figure 2 is aplan view,

""Flgurel is a a Asverse sectienftaken Ion? the A line 34"-3 ofFigureil. Y

' Flsui'e'ii` is a rear end' eleyatio laljv'iew broken awayinparty"`A il Figure 5 is a fragmentary sectional plane taken inyentiomt A v .t fj'Figure V'- is a longitudinal mid-sectional elevafurther modinedform ofthe invention.

The'injection molding of plasticsinvolves` con-'j e 8 is` a, transversesection on the line `rtiunding saidcylinder `having arranged thereinf tHans for maintaining afconstant temperature" A about'thecylinderinconiunctionwith awhollow l tapered body located within thecylinder and havits interiorkcommunicating--withtheinterior n Vof thejacketlor with a Iseparately'controllable-V e heating unit forcirculating a heatingmedium @therethrough i f l body of recentieaifneuity in maintaining thmesifed uniform4 degree of duction of amolded productoihighlquality and uniformity,

AInjiny earlier Patent 2,115,940 'datd May 3 -lf9'38g1have disclosedaheating means for plastic "injection cylinders wherein junit arrangedwithin ajacket encircling the iniection cylinder Vmaintains thecylinder-fin `a I (heated condition-'bythe application"4 of" steam y"thei'eabQUtt Thisimanner' of heating vtheinjectioncylinder t proventolbe ei'rtremely eiiicient` and dependble in` practice -and hasalleyiatedrthe dimculty previously experienced maintainingv` a 'uni-Lforxri; operating temperaturev such as when direct temperature andplasticitylthroughout'themass in order to ensure the prol 'only aboutthe` lan electric `heater "heating: .or the ycylinder or associatedparte bytlectrical resistance heatersfwer'e attempted:

:The present invention proposesastlll further` "i'mjiarovement"iny theprovision for the circulation leigexuntaheetme medium not injectedor.ertrutiedistensedA to and extensive surface `contact -so that theplastic will be subjected tota definitely controlledtemt 1l Yat the topand ,With this arrangement'itgwill beseen that the steam or vapourwithin the interlorof the casingV `and pass intothe cylinderand'aboutwhich the material" to fbej pStllnintimlte peratureyortemperatures interiorlyas wellas `exteriorly 'without attiie same'time 4iIlYQlyinZ'- the possibility of overheating or `burning or foul-ging the die orince as is possible in the use of' directly appliedresistance heaters. t

l -In the form of construction illustrated inFig- -Y ures l'to 5 aninjection cylinder l extends through and is-jacket'ed by a casing 21formed w'vithA a Y downwardly dependinghollow extension 3 which t formsasumpl chamber 4` withiirwhichis placed a quantity of water or othersuitable vapourizablefluids. t A a A suitable type ofelectricalimmersiohheater 6 is arranged in the sump 4 in contactwith the fluid i tovapouriz'e the same, and the illl the interior of thecasing 2,

vapour is caused to v the cylinder; to

includingy the space 1 .about e effectively heatthe cylindersubstantialiyin theV ymanner set forth in my earlier patent aboyereferredtm. t

Located within the cylinder I is afhollow .elongated tapered body thevihzite irorwerd tapering end converginginto close proximity to theiniectionior extruding orice 9. The member I'is provided=withsupportingand positioning t' bosses III of elongated tapering form whichl snug-1y nt r je .cylinder 4, and tubular` ducts Il are insertedthrough thel cylinder wall end extend inwardly through thelsupoortingportions] t!l of the member l and establish communil cationbetweeritheinterior of the jacket casing 2 andthe interior l2 oi the inner hollowmember bottom'oithe cylinder.

`2 will .be free to enterthe upper tubular ductll n interior Vof theAhollowmember 8 to efiect an extensive heatinterchange with the innerAwall .surface thereof. v. and condensation ,formed within the member 8will pass out through the lower tubulardiucij.` I I land is preferablyAcorrductedsftothe lower level ofthe sump 4 by a tubular extensionpii. f1` It desired the 'supportingbosjs members I0 may be .of rhollow`formation 'as "indicated in dotted lines' Figure "5in orderlto'furthertincrease'the 1heatexchange surface available tothe highlyheated steamA or vapour "withinj, the "cylinder The .heating uniti;Vwill Apreferemy*he oon- .trolled` by .a suitable thermostat notv shown)inserted `in an orifice Il inthe upper portion of the-'jacket 2; and apressure gauge .l5 is con- "nect'ed with the interior ofthe-jacket by aitubular NTFQFFIICB- e side ofthe injection-or `extrusion cylinder butalso within ehelio-rr'` body located `within the 2 conduit I6. A plug I1is preferably threaded into the casing 2 to enable the charging of thevapourizable liquid 5 thereinto.

In the operation lof the device the cylinder I will be charged with asuitable quantity of theV moves toward the ejection orifice 9 it will bethinned out into a thin stratum while absorbing heat on the inward sidefrom the heated member 8 and on the outward side from the heatedcylinder I, so that when it reaches the orifice 9 it will be uniformlyAheated at exactly the required temperature, therebyA ensuring uniformmolding results.

Referring vto the modic'ationof Figure 6, the hollow body 8 insertedwithin the cylinder I is shown provided with a rearward cylindricalextension I9 concentrically disposed in the cylinder and encircled by asleeve-like piston which is adapted to be advanced by a hydraulic.piston 2l operating in a cylinder 22. i

The tubular piston 20 thus serves to support the rearward end of thehollow member 8', and whenthe piston 20 is withdrawn at the chargingorifice V23 the cylinder I' willv be' charged with the material from thesupply 24, after which thereturn movement of the piston 20 will forcethe charge of material into the vapour-heated zone to be effectivelyplasticiZed and subsequently ejected through the orifice 9.

VIn the further modification illustrated in Figure 7 I have shown ahollow body 8" *concentrically positioned at its forward end within thecylinder I by a series of longitudinally tapered ribs intimately fittingthe interior surface of the cylinder and supported at its rearward endby the tubular piston 20 which is adapted to operate in the manner ofthe piston 20 defined in Figure 6. y

The rearward extension I9' of the hollow member 8" is here shownprovided with passages 25 and 26, one above the other, within whichconduits 21and28 are inserted.

A separate heating unit 29 is'provided .corn-Y prising va hollow casingcontaining a body of water or other'vapourizable'liquid 5', this beingvapourized by an electric heating unit 6' which maybe suitablycontrolled so that the temperature of the vapour produced will have adesired predetermined relation to the temperature'of the vapour producedwithin the casing 2 by theheating unit. 6. y

lThe conduits 21 and 28 connect'with the interior of theheater casing 29and the heated vapour is adapted to flow mainly through the upperconduit 21 into the interior of the'hollow member 8" and condensationwillreturn through thelower conduit 28 back to the unit 29.

- Y The combination defined in vconnection with Figure '7 will beparticularly advantageous in the handlingvof certain plastics or whereitis essential to maintain a temperature difference between the cylinder Iand hollow member 8*", or to compensate for differences in the rate ofheat radiation from the cylinder I or element 8".

The constructions defined will eliminate difliculties .in the extrudingor injection molding of plastics', and while I have shown specificstructures by way of illustration of the present invention, it will beunderstood that the invention is capable of further modifications orstructural interpretations within the essential spirit thereof.

While the present invention represents a particularly important advancein the art of injection molding of plastics wherein the plastic isforced under high pressure into previously prepared mold cavities, itwill nevertheless be advantageously applicable in connection with -theextruding of continuous strips of material capable of being softened orplasticized in the manner dened.

What I 'claim as my invention is:

1. In apparatus of the class described a jacketed cylinder provided witha discharge orifice and means for forcing a plastic from said cylinderthrough said orifice, means for effecting the circulation of a heatingfluid both internally and externally of said cylinder, including ahollow member disposed within the discharge end of said cylinder, andmeans forming a path of circulation betweenthe interior of said holloilrmemberand the jacket space of the cylinder, to maintain substantiallyuniform temperatures therein.

2. In an injection molding apparatus for plastics, an injectioncylinder, means forming a heating jacket about said cylinder, saidjacket containing a quantity of vapourizable fluid, and means forvapourizing said fluid, the combination therewith of a hollow taperedbody disposed within said cylinder, andv means for supporting saidhollow body within said cylinder including tubular ducts extendingthrough the wall of the' cylinder and hollow member and formingcirculating passages solely between the interior of the 4jacket'and theinterior of the hollow member.

3: Apparatus as claimed in claim 2 in which the means for supportingsaid hollow member within the cylinder includes elongated taperingbosses through which said tubular ducts extend, said bosses beingsurfaced to conform with the cylinder surface and engaging the innersurface of the cylinder in snug sealing and positioning contact, saidtubular ducts comprising short tubular elements sealingly insertedthrough the bosses and adjacent portions of the jacket wall andterminating entirely within the space enclosed bythe outer jacket wall.

4. Apparatus as claimed in claim 2 in which said tubular ducts arearranged one above the other, the upper duct connecting the vapourspaces of the jacket and hollow body, said jacket being provided with asump for a vaporizable fluid, and a tubular drain duct leading from thelower tubular duct to a point in said sump below the level of thevaporizable uid therein.

5. In an apparatus of the class described comprising a cylinder having adischarge orifice, pressure means for ejecting a plastic from thecylinder,.a sealed jacket spaced from and surrounding said cylinder, achamber depending from said jacket, adapted to contain a body of waterand communicating with the space about said cylinder and an immersionelectric heater arranged in said chamber and adapted to Vbe surroundedby said body of water and to generate steam, the combination therewithof Vmeans for circulating within the cylinder a portion of the steamgenerated to maintain substantially `uniform temperature conditionsinteriorly and exteriorly of said cylinder and ensure uniformplasticizing of the contents vbeing ejected therefrom.

ARTHUR A. BURRY.

